GB2258417A - Mass production of discs from sheet materials with minimal waste - Google Patents

Abstract

The process produces in two or more stages from strip 10 or sheet material circular discs, polygons or lobed shapes. The process applies to any malleable material and reduces the waste of conventional blanking. Asymmetrical squares or hexagons which tesselate are cut by progressive notching and/or cropping. The shapes give complete separation and permit errors in feeding the material. Waste only arises at the sides of the strip, in the case of hexagons. For malleable materials the parts are compression extruded between punch and dies considerably thinning, enlarging and forming the discs into circles, polygons or lobed shapes, within the die or punch profiles. Pressures of extrusion can be reduced by conically pointed punches. Conical indents in the discs can be avoided by special punches in which the conical points flatten due to the final high pressure. The punches are within the invention. For harder materials the parts are roll rimmed reducing the corners towards circular or lobed forms as desired. Alternatively the rounding can be done by punch and die sinking. Both techniques use special tooling within the invention. <IMAGE>

Description

MASS PRODUCTION OF DISCS FROM SHEET MATERIALS WITH MINIMAL WASTE 1. This invention is a process producing circular discs, regular polygons or lobed shapes with little or no waste from strips or sheets of material by cutting and forming techniques. The parts produced may be coins, mechanical or electrical components used in assemblies, or items of food. The parts may be further formed and extended from flat material into raised shapes such as cans, or fixed by pressure welding to other separately made components. The process can be applied to any malleable material which can be extruded under compression including plastics, foods and metals, allowing many diverse applications.

2. The traditional method of producing circular discs is be blanking from strips or sheets of material. The remaining material needs sufficient strength not to twist when cut nor to collapse for controlled movement out of the tooling. This material is waste which can be reclaimed but this involves significant equipment, processing plant and hence cost. Waste is usually between 20-40% of the initial strip or sheet.

3. In contrast to the above the invention produces circular discs or regular polygons of more than four sides or lobed shapes from strip or sheet material in two or three stages depending on its malleability and friction with the tooling as follows:3.1 Cutting asymmetrical squares or asymmetrical hexagons by progressive notching and/or cropping. The modified forms ensure the parts are separated and overcome small errors in feeding the material which otherwise spoil the process of cutting accurate squares or hexagons.

3.2 Malleable materials are cut into modified squares or hexagons relative to the final discs smaller in widths (less than 80%) and to be the same volume much thicker (greater than 160%) than the final discs. These are extruded by compression in punch and die tooling, reducing the thicknesses and so expanding the perimeters which become or tend to become circular, due to two#factors; the tension in the perimeter, secondly the radial lengths to the flats is less than those to the corners giving the former less resistance to deformation.

3.3 The inner walls of the die cavities can be shaped to form the discs into polygons or lobed shapes.

3.4 The pressures necessary for extrusion can be greatly reduced by convex conical points on the faces of the punches, but these leave conical indents in the blank produced. If the blanks must be flat and parallel in thickness the indents can be avoided by the cones on the punches becoming flat at the last part of the pressing action. These special tools are within the invention.

3.5 Harder materials the same thickness as the final discs are cut into modified hexagons these are either rim rolled, compressing the corners towards a rounder form or alternatively the rounding can be done by punch and die sinking using special tooling in both cases, which are within the invention.

4. Raised profiles such as coining are produced by the profiles in the faces of the punches as normal.

5. Raised cans can be produced by the punch and die having clearance allowing the material after expansion to extrude forward and/or backward relative to the punch movement.

6. Cold welding of the parts to separate parts is possible if the latter are inserted into the tooling into which the squares or hexagons are extruded to the desired shape set by either the punch or the separate part. This limits further expansion, greatly increasing interface pressures and temperatures so that welding occurs.

7. If the material is a solid with no significant voids its volume is not changed, so that the larger area has a correspondingly thinner section. Compression of the material introduces strain energy which usually converts to heat, raising the temperature, particularly if performed by impact in a very short duration of time, this reduces the yield stress and the applied force and energy required as an additional advantage.

8. The invention will now be described to show by examples the applications of the principles to produce specific discs or products, and using special tooling. These are illustrated by the following drawings:9. Fig 1 Shows the basic layout of a tool to notch and crop nine modified square blanks.

10. Fig 2 Shows to a larger scale the details of punch shape and position in Fig 1.

11. Fig 3 Shows the basic layout of a tool to notch and crop, seven modified hexagonal blanks.

12. Fig 4 Shows to a larger scale the details of punch shapes and positions in Fig 3.

13. Figs 5 & 6 Show a punch assembly with a cone collapsing to a flat, spring loaded internally by an elastic solid. The blank is shown is three cross sections beneath.

14. Fig 7 Shows a punch assembly with a cone collapsing to a flat spring loaded internally by disc springs.

15. Fig 8 Shows the basic machine parts to roll rim the blanks of hexagonal form.

16. Figs 9 & 10 Show two sections showing the profiles taken from centre axis of the machine in Fig 8.

17. Figs 11 & 12 Shows linear developments of the profiles of the capstan drum and the former segments with the hexagonal blanks being formed into circular blanks.

18. Figs 14 & 15 Shows cross sections of the tool for pressure die sinking the modified hexagonal blanks.

19. Figs 1 & 2 The strip 1 is guided between guides or rollers 2 & BR< 3 to stops at 4. A guillotine blade 5, crops five blanks 7.

A line of punches 6 cut on three sides giving four blanks.

The sides of slots 8 are cut in the previous cutting stroke by punches 6.

20. Figs 3 & 4 The stip 10 is guided between guides or rollers 11 & 12 to stops at 14. A guillotine blade 15 crops four blanks 13. A line of punches 16 cut on five sides giving three blanks. The sides 18 are notched by punches 17 whilst sides 19 of the slots are cut in the previous cutting stoke by punches 16.

21. Figs 5 & 6 The blank starts as either a modified square or hexagon 20, is extruded to 21 by the cone point of the punch 24 which collapses under high pressure to flat 25, completing the extrusion of the blank 22. The outer part of the punch 26 is a long can with slots 29 to allow flexing and a top flange. The ring 30 raises the can to compress the inner elastic part 28 against 31 and 33 the upper plate of the tool. The ring 32 locate radially 30 and 31. A tube 27 contains 28 from radial expansion. When extruding against the blank the press acts on 33, 31, 28 and 24 or 25. The outer can provides a smooth polished face on its bottom surface to reduce friction and wear.

22. Fig 7. Shows a punch assembly suitable for mass production using disc springs. The basic function of the assembly is that of the punch in Figs 5 & 6. The cone point of the punch 35 collapses under high pressure to flat 36, to complete the extrusion of the blanks. The outer part of the punch 37 is a can with vertical slots to allow flexing at 38. The small disc springs 39 support 35 or 36. The initial force is supplied by 40, 41 and the large disc springs 42. When the outer can 37 flattens as 36 outer parts 43, 45 and 46 transmit the greater part of the force from the press. Adjustment of the initial force giving a cone is possible by replacing some of the springs 42 by a solid spacer.

23. Figs 8, 9, 10 11 & 12 The modified hexagonal blanks 50 enter on a chute 51 by rolling or sliding on the outer wall. The chute may be substituted by a feeder of other form such as a wheel or reciprocating slide. The capstan or drum head 52 revolves clockwise carrying the blanks in a slot to engage with the segment 53, so that the blanks are rotated anti clockwise against the segments. The serrations 54 catch the corners to increase the grip and deform the corners reducing the widths of the blanks. Part of the segment 55 is slightly tapered relative to the Capstan and finally parallel to give a circular form to the blanks 57. The blanks are picked out by a wedge blade 58 and ejected into a chute 59.

24. Figs 14 & 15 shows the hexagonal blank 60 after feeding into the tool by a wheel 61, laying on punch 62 beneath and pressed down by the upper punch 63 into a disc ring 64 having a bore with taper and parallel sections. The force of the press aboe acting through 65, 66 and 63 presses the blank down through the die which presses the corners of the blank to a circular form. Due to the upward force from the punch beneath the material in the blank is restrained within the empty spaces outside the flats of the hexagon. Upward thrust is provided by the part 68. The punches 62 and 63 have circular faces engaging with the blank but are slotted 69 to allow expansion and contraction which also aids the movement of the material in the blank.

Claims (4)

1. A process to produce circular discs or regular polygons of more than four sides or lobed shapes from strip or sheet material in two or three stages depending on malleability and friction with the tooling; cutting asymmetrical square or asymmetrical hexagons by progressive notching and/or cropping; malleable materials are cut into modified squares or hexagons relative to the final discs smaller in widths (less than 80%) and to be the same volume much thicker (greater than 160%) than the final discs.These are extruded by compression in punch and die tooling, reducing the thicknesses and so expanding the perimeters which become or tend to become circular; the inner walls of the die cavities can be shaped to form the discs into polygons or lobed shapes; special punches having faces to press onto the blanks of convex coned shape that flatten at the final part of the extrusion giving flat parallel discs; harder materials the same thickness as the final discs are cut into modified hexagons these are either rim rolled, compressing the corners towards a rounder form or alternatively the rounding can be done by punch and die sinking using special tooling in both cases, which are within the invention.

2. A process as Claim 1 with raised profiles on the punches producing raised profiles on the discs or shapes.

3. A process as Claim 1 in which the parts enlarge and further extrude either or both backward, above or forward beneath the discs or shapes, giving single or double cans.

4. A process as Claim 1 wherein the said squares or hexagons of the said material are pressed, formed into discs, polygons or lobed shapes and bonded to other parts other than the said shapes whilst in the tooling means.